The neoplastic lymphocytes of the cutaneous T cell lymphomas have T cell membrane features and a distinctive tissue distribution (preferential skin infiltration, localization in T cell zones of lymphatic tissue and bone marrow sparing). The leukemic phases of these lymphomas provide unique opportunities to correlate properties of the neoplastic cells with specific clinical manifestations of the disorders. The proposed studies have three interrelated objectives: 1) To determine whether the recirculating nature of the neoplastic cells of the cutaneous T cell lymphomas can be used to therapeutic advantage, clinical trials of leukapheresis will be expanded. 2) To identify tumor and tissue-specific antigens (characteristic of the helper T cells from which the neoplastic T cells appear to be derived), leukemic T cells obtained in large quantity during leukapheresis will be used as reagents. Heteroantisera, produced by immunizing rabbits with leukemic T cells, and naturally occurring anti-T cell sera, from patients with lupus erythematosus and pemphigus vulgaris, will be absorbed with B cell lymphoblasts, erythrocytes and liver. The antisera will be further purified by application to and subsequent elution from immunoabsorbent columns containing membrane fragments of leukemic T cells conjugated to Sephadex G-100. The specificity of the recovered antibodies will be determined by 51Cr release cytotoxicity, fluorescence microscopy, fluorescence-activated cell sorting and inhibition of individual aspects of normal T cell function. 3) The basis of the interaction between the neoplastic cells of the cutaneous T cell lymphomas and the skin will be investigated. Epidermal cells will be used as targets in cytotoxicity studies to determine whether the neoplastic T cells are autoreactive against keratinocytes. Extracts of skin will be tested for lymphocyte chemotactic properties. The effect of epidermal cells on T cell differentiation will be examined to determine if skin can support T cell maturation. Together, these studies are designed to identify the biologic significance and clinical relevance of the special features of the neoplastic cells of the cutaneous T cell lymphomas.